Sheet cutting apparatus

ABSTRACT

Sheet cutting apparatus powered wholly by hydraulics including a blade for cutting and a hydraulically operated clamping bar for holding the sheet material in place for cutting after clamping has been effected.

Elmitefl States Patent Krauss Aug. 28, 1973 [54] SHEET CUTTING APPARATUS grac:1ey. ..l.l. 83/2325);

, es en'elc er lnvemofi Edward William Krill, Skokie, 3,501,988 3/1970 Morelli 83/639 x 3,410,166 11/1968 Thumim.... 83/461 X [73] Ass'gnee' IPEC lnmmmed ohms 968,196 8/1910 Reeder 83/639 x [22] Filed: Oct. 7, 1971 Primary Examiner-Andrew R. Juhasz [21] Appl' 187324 Assistant Examiner-James F. Coan Attorney-Charles A. Laff et a]. [52] [1.8. CI 83/380, 83/390, 83/461,

' 83/639 57 ABSTRACT 51 lm. c1 826d 5/42 58 Field 61 Search 83/461, 374, 375, Sheet p s apparatus powered Wholly y hydrauhcs 83/390, 452 39 53 379 3 0 331 mcludmg a blade for cuttmg and a hydrauhcally operated clamping bar for holding the sheet material in 5 References Cited place for cutting after clamping has been effected.

UNITED STATES PATENTS 3,289,514 12/1966 Rupp 83/461 X 7 Claims, 8 Drawing Figures SHEET CUTTING APPARATUS BACKGROUND The present invention relates to apparatus for cutting sheet material, and more particularly to cutters having hydraulically power-operated blades for simultaneously cutting many sheets of paper, fiberboard and the like.

In the past, paper cutters have generally been electrically operated. Because of the complexity of the electrical circuits necessary to control and operate these cutters, these cutters were expensive. Also, breakdowns frequently occurred so that maintenance and repair was costly; and short-circuiting could sometimes cause unexpected operation which in some instances could cause serious injury to the operator.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a sheet cutting apparatus which is relatively safe to use, inexpensive, and requires a minimum of repair and maintenance. It is a further object to provide a cutter which is powered wholly by hydraulics, rather than by electrical power. It is a further object of the present invention to provide such a cutter in which the length of the stroke and the attitude of the cutting blade are readily adjustable. Another object of the present invention is to provide such a cutter in which the anvil is readily replaceable.

A further object of the present invention is to provide a sheet cutting apparatus equipped with a hydraulically power-operated clamp, and with means for automatically operating the clamp before the cutting blade can cut the sheet material. Another object of the present invention is to provide a sheet cutting apparatus in which the clamping apparatus may beoperated alone I become manifest by an examination of the following description and accompanying drawings.

In one form, the invention consists of a sheet cutting apparatus having a horizontal bed for supporting a stackof sheet material, such as paper sheets, means for supporting a cutting blade for movement in a vertical plane, hydraulically operated means for urging said cutting blade downwardly toward said bed, hydraulically operated clamp means for clamping said sheet material in position on said bed, and means for causing said hydraulic clamping means to become operative prior to the operation of said cutting blade which include two spaced-apart controls adapted to be manually operated. These controls must be simultaneously actuated to initiate operation of the clamp and blade. In this way the machine operator must use both hands and is thereby prevented from accidentally cutting one of his hands. The apparatus is powered entirely by hydraulics, the sole nonhydraulic component being an electric driving motor for, among other things, driving the hydraulic pumps, and such lighting as may be required.

DESCRIPTION OF THE DRAWINGS Reference will now be made to the accompanying drawings in which:

FIG. 1 is a front elevation of an exemplary embodiment of the present invention;

FIG. 2 is a side elevation of the apparatus of FIG. 1;

FIG. 3 is a rear elevation of the apparatus of FIG. 1;

FIG. 4 is a plan view of the apparatus of FIG. 1;

FIG. 5 is a perspective view of a portion of the apparatus of FIG. 1, showing the interrelationship of the cutting blade and the anvil, and the mechanism for ejecting the anvil;

FIG. 6 is a partial vertical cross section of the apparatus of FIG. 5, taken along the section line 6-6;

FIG. 7 is a schematic circuit diagram of the hydraulic system associated with the apparatus of FIG. 1; and

FIG. 8 is a crosssectional view of a hydraulic cylinder employed in the apparatus of FIG. 1.

DESCRIPTION Referring now to the drawings, and especially to FIGS. 1-4, there is shown a sheet cutter 9 having a sheet-supporting bed 10 supported by a hollow frame 12, preferably formed of sheet metal which is welded together. Within the frame 12 are contained tanks 14 and 16, for storing hydraulic fluid used in the operation of the cutter. The frame 12 also houses two pumps 200 and 206 (FIG. 7), by which the hydraulic fluid is pressurized, and an electric motor 210 for driving both of the pumps, as well as other apparatus associated with the hydraulic control system. Access to the apparatus is obtained by means of a door 13 hinged so as to open toward the front of the frame 12.

Located above the bed 10 and supported on the frame 12, is an upper housing 18, formed of two side walls 20 and 22, interconnected at their top edges by an upper wall 24. A vertical bulkhead 26 is located within, and welded to, the walls 20, 22 and 24. The bulkhead 26 supports a cutting blade 30 and a clamping bar (see FIG. 3). The clamping bar will be hereinafter described in greater detail. The central area of the lower part of the bulkhead 26 is provided with an opening 28, so that sheet material maybe moved on the bed 10 from one side of the bulkhead 26 to the other, and thereby be brought into the area of operation of the cutting blade 30 and the clamping mechanism 80.

A pair of brackets 32 and 34 are secured to the top of the cutting blade 30. The bracket 32 has a pivot pin 36 which is pivotally connected to the lower end of a link 38. The upper end of the link 38 is pivoted to the bulkhead 26 by means of pin 40. The bracket 34 is provided with a pin 42 pivotally connected to the lower section 45 of a link 44. The upper section 47 of the link 44 is pivotally connected to a pin 46 supported on the bulkhead 26.

By means of the links 38 and 44, the blade 30 may swing about the axes of pins 40 and 46. As it swings downwardly from its upper position, shown in FIG. 1, it executes a slicing movement, ending with the bottom or cutting edge 50 of the blade 30 in the plane of the upper surface of the bed 10.

The attitude of the blade 30 is adjustable by means of a connector 48 which joins the two sections 45 and 47 of the link 44. Preferably, the connector 48 is threadedto each section of the link 44, with the threads on each section being of reverse pitch, (in turnbuckle fashion), so that turning the connector 48 relative to the axis of the link 44 in one direction serves to lengthen the link, whereas turning the connector 48 in the opposite direction serves to shorten the link 44. In this way, parallelism of the lower edge 50 of the blade 30 with the surface of the bed 10 may be maintained, even though the blade 30 may wear at different rates along its length. The blade 30 is biased towards its upward position, as illustrated in FIG. 1, by means of springs 52 and 54. Spring 52 is connected at its lower end to a bracket 56 mounted to the side wall 20, and at its upper end to a bracket 58, which is secured to the top of the cutting blade 30. Spring 54 has its lower end connected to a bracket 60 mounted on the side wall 22 and its upper end is connected to the bracket 34 secured to the top of the blade 30.

The bracket 32 is provided with a second pivot pin 62, to which is connected the lower end of the operating shaft 64 of a hydraulic cylinder 66. The cylinder is pivotally connected to the bulkhead 26 by means of a pin 68. Hydraulic cylinder 66 furnishes the power to drive the cutting blade 30 downwardly toward the top surface of the bed 10. As the hydraulic fluid is supplied to the cylinder 66 by way of line 71, a piston within the cylinder is forced downwardly, the force of this piston is transmitted through the shaft 64 to the bracket 32,

and the blade 30 is thereby moved downwardly. The

blade 30 continues its downward movement until the piston within the cylinder 66 reaches the end of its stroke, at which point further movement is arrested. The stroke of the piston within the cylinder 66 may be adjusted by means of a control wheel 70, in a manner described hereinafter with reference to FIG. 8.

In FIG. 3 the rear of the machine is illustrated. A pair of vertical guides 72 and 74 are mounted between the top of the frame 12 and the lower surface of the upper wall 24. Slides 76 and 78 are slideably mounted on the guides 72 and 74, respectively, and the clamping bar 80 is connected between the slides 76 and 78. The clamping bar 80 is formed of rigid material for effective gripping and clamping of a stack of sheet material to the bed 10. A plurality of ribs 81 extend rearwardly from the bar to distribute the clamping force rearwardly over the surface of the stack.

Motive power for lowering the clamp bar 80 is furnished by either one of two hydraulic cylinders 82 and 84, both of which are connected between the clamping bar 80 and the top wall 24. Hydraulic cylinder 82 is a low pressure cylinder and the cylinder 84 is a high pressure cylinder. The cylinder 82 is operated when a small clamping force is desired, so that the stack may be adiusted in its position prior to cutting. The cylinder 84 IS operated as part of an automatic sequence in which the stack is first clamped and then cut by operation of the blade 30.

Parallelism of the clamp bar 80 with the bed is assured by means of a regulating mechanism, including a bell crank 86, pivotally mounted to the surface of the bulkhead 26 by means of a pin 88, and a bell crank 90, pivotally mounted on the surface of the bulkhead 26 by means of a pin 92. One end 94 of the bell crank 86 is connected to one section 95 ofa link 96. The other section 97 of the link 96 is connected to an end 98 of the bell crank 90. The end 100 of the bell crank 86 is connected by a link 102 to the clamp bar 80, and the end 104 of the bell crank 90 is connected to the clamp bar 80 by a link 106. The length of the link 96 is adjustable by means of connector 108, interconnecting the sections 95 and 97, which is similar in its construction and operation to the connector 48 illustrated in FIG. 1.

The clamp bar 80 is biased toward its upward position, shown in FIG. 3, by means of springs 110 and 112. The lower end of the spring 110 is connected to a bracket 114, mounted on the slide 76, and the upper end of the spring is connected to the upper wall 24. The lower end of the spring 112 is connected to a bracket 116, secured to the slide 78, and the upper end of the spring 112 is secured to the upper wall 24. By means of the springs 110 and 112, the clamp bar 80 is urged towards its upper position until one of the hydraulic cylinders 82 and 84 is actuated.

As best illustrated in FIG. 4, the bed 10 is formed of two parallel slabs 116 and 118, which are supported in spaced-apart relationship. A bar 119 is connected preferably by welding, between the slabs at the front end of the machine, and a bar 120 connects the slabs at their other ends. A plurality of additional bars 121 are connected preferably by welding, to the slabs I18 and 119, and extend inwardly nearly to the center of the space between the slabs 116 and 118.

In the space between the slabs 116 and 118, near the inward ends of the bars 121, a cylinder 123 is located, with an end secured to the bar 119 by means of a bracket 124. An actuating shaft 125 of the cylinder 124 extends toward the other end of the machine and is connected to a bracket 126 secured to a pusher plate 128, supported by the slabs 116 and 118.

The bracket 126 has connected thereto a tubular guide 130, adapted to slide on a guide shaft 132 supported between the bars 119 and 120.

When the cylinder 123 is actuated, it draws the shaft 125 forward and moves the pusher plate 128 toward the cutting blade 30. Sheet material which is to be cut is thereby carried toward the blade 30.

Referring now to FIG. 5, the slabs 116 and 118 are interconnected with a U-shaped body having side walls 142 and 144 and a bottom wall 146. Preferably the U- shaped body is welded together and welded to the slabs 116 and 118 so that they form a rigid assembly. A pair of elongate L-shaped brackets 148 and 150 extend along the length of the side walls 142 and 144, and are welded thereto. The brackets support a rigid, unyield ing plate 152. Two rectangular plates 154 and 155, preferably formed of a hard plastic material, are located above plate 152. The top plastic plate 155 serves as the anvil for the cutting blade 30, and the bottom plate 154 serves as a spare anvil and also resiliently supports the anvil 155. The unyielding plate 152 forms a rigid base under the assembly.

The cutting blade 30 compresses the sheet material to be cut between its cutting edge and the anvil 155, and, as a result, the anvil 155 eventually becomes scarred in the area immediately under the cutting edge 50 of the blade 30. Preferably, this area is offset from the center of the anvil 155, so that when the anvil 155 is removed and rotated about a vertical axis, it can be replaced to provide a new surface directly under the cutting blade 30. In addition, the opposite side of the anvil 155 may also be used (in two different attitudes) so that a single anvil 155 may be employed in four different arrangements to provide four new surfaces under the cutting blade 30.

When it is desired to remove the anvil 155 for readjustment or replacement, an expandable tube 156, located in the area between the plate 152 and the walls 142, 144 and 146, is expanded by application of a suitable hydraulic force, which forces the plate 152 upwardly, thereby bringing the anvil 155 into a position above the surface of the bed 10. In this position the anvil 155 may be readily turned over or replaced with a new anvil, as the need may be.

FIG. 6 shows the expandable tube in expanded condition, with the anvil 155 raised above the level of the bed 10.

Referring now to FIG. 7, there is shown, in schematic form, the hydraulic circuit associated with the sheet cutting apparatus. A pump 200 furnishes high pressure fluid to an outlet line 201. It communicates with a sink 202 by means ofa filter 203, so that hydraulic fluid may be drawn into the pump through the filter 203 and furnished to the output line 201. A relief valve 204 passes fluid from the line 201 back to the sink 202, in order to establish a predetermined maximum pressure on the line 202. The volume of pressurized fluid produced by the pump 200 is, however, limited, so that when one of the power cylinders is being operated, the pressure in the line 201 is less than the maximum value determined by the relief valve 204.

The second pump 206 communicates with the hydraulic fluid in the sink 202 through a filter 207, and furnishes pressurized fluid on a line 208. A relief valve 209 is provided to establish a predetermined maximum pressure in the'line 208, which is substantially less than that in the line 201.

The two pumps 200 and 206 are both powered by a motor 210 by connections shown by the dashed line 211.

The control system of the present invention incorporates two manual hydraulic valves 212 and 214. The valve 212 is the primary control valve, and the valve 214 is the secondary control valve. Both valves must be operated simultaneously, and they are positioned on the machine so that both of the operators hands are necessary to actuate the valves at the same time. This insures that the cutting operation occurs only when the operators hands are outside the vicinity of the cutting blade.

The valve 212 has a body 213 and a control member 216 (see FIG. 1) by which valve 212 may be operated. When the cutting blade 30 is to be operated, the member 216 is pushed downwardly (as viewed in FIG. 7) by one of the operators hands. Simultaneously the control member 218 of the valve 214 is also manually pushed into energized condition (rightwardly as viewed in FIG. 7), in order to complete a connection of pressurized hydraulic fluid to the clamp mechanism and to the mechanism for powering the cutting blade 30. As shown in FIGS. 1 and 2, the control member 216 is located under the forward end of the bed 10, beneath the bar 119, while the control member 218 is located on a guard member 219, secured between the frame 12 and the wall 24, forwardly of one end of the blade 30. An identical guard member 220 is secured to the frame 12 forwardly of the other end of the blade.

When the valve 214 is in unactuated condition, it connects the line 201 through a normally open valve 221 to a line 220 which leads through the valve 214 to a line 224 and to a sink 222. The sink 222 communicates directly with the sink 202 to return hydraulic fluid to the intake of the pump 200.

When the valve 214 is actuated, pressurized fluid is conducted to line 226 and thereby to an inlet port 228 of the valve 212, and to the inlet passageway 244.

Connected to the control member 216 of the valve 212 is a shaft 230 which extends downwardly, as shown in FIG. 7, and which has a plurality of spools which control the sequence of operation of the several functions of the valve 212. The spools are all connected rigidly to the shaft 230 and operate both to limit the position of the shaft 230 from time to time, and also to open and close passageways for hydraulic fluid.

Before the valve 212 is operated, a chamber between two spools 231 and 248 connects an inlet passageway 244, which communicates with the inlet port 228, with an output passageway 232. The outlet passageway 232 leads to a line 233, which in turn is connected to a sink 262.

When the member 216 is initially depressed, the shaft 230 moves downwardly, and the spool 231 closes the passageway 232. Downward motion of the shaft 230 continues until a spool 232 comes into engagement with a pin 234. The pin 234 is connected to a piston 236, resiliently urged inwardly of the valve body 213 by means of spring 237 disposed in a chamber provided in the body 213. The downward movement of the shaft 230 is sufficient to enable a spool 238 to clear the entrance to a passageway 239 which leads to an output line 240, and hydraulic fluid is thereby permitted to flow from the line 226 through the valve 212 to the line 240. A spool 246 seals the top end of the valve 212. The line 240 is connected to the cylinder 84, which powers the clamping mechanism as described above. The cylinder 84 is energized to clamp a stack of sheet material on the bed 10 in a position to be cut by the cutting blade 30, a piston 242 within the cylinder 84 forcing its actuating shaft 243 outwardly, and lowering the clamping bar 80 (FIG. 3).

The volume of space within the cylinder 84 increases as the piston 242 is forced out of the cylinder and prevents the pressure of fluid on the line 240 from rising to the level set by the relief valve 204. The pressure is therefore kept at a relatively low level until the clamping bar 80 reaches the top of the stack of sheets to be cut, and clamps the stack to the bed 10. Then the volume of the cylinder 84 ceases to expand and the pressure of the fluid rises. The inlet port 228 is connected by means of a passageway 244 within the valve 212 to the chamber in which the piston 236 is located. The rising pressure of the hydraulic fluid in the line 226 forces the piston 236 outwardly against the force of the spring 237, and withdraws the pin 234 from the path of the spool 232. Thereafter the control member 216 may be moved further downwardly to initiate the next function, which is the actuation of the cutting bar 30. The spool 233 seals the bottom end of the valve 212.

As the shaft 230 resumes its downward movement, spool 248 opens the inlet passageway 244 to a chamber between spools 248 and 231, which leads to a passageway 250. Outlet from the passageway 250 is normally blocked by a piston 252, urged upwardly by a spring 254, disposed in a chamber within the valve body 213. Increased pressure on the line 240, when the clamping bar 80 has reached the top of the stack to be cut, causes the piston 252 to move downwardly in its chamber and open a path from the passageway 250 to an output line 70. The output line is connected to the cylinder 66 so that the piston 258 within it is moved outwardly, thereby causing the cutting blade 30 to be forced downwardly toward the bed 10 (See FIG. 3).

The piston 252 insures that there is adequate pressure in the line 240 whenever the cutting blade is operated. This prevents the cutting blade from being operated until after appropriate clamping force has been applied to the clamp bar 80, and insures that there is sufficient pressure available to operate the cutting blade properly.

When the cutter bar 30 reaches its lowermost position, in which the edge 50 is located in substantially the same plane as the top surface of the bed 10, the valve 221 is actuated by a control member 258, interposed in the path of the bracket 58 (see FIG. 1). The valve 221 thereby senses when the edge 50 of the cutting blade 30 has reached its final position. Actuation of the valve 221 cuts off the communication between the line 201 and the line 220, and instead connects the line 220 with a line 260 so that fluid may flow in reverse direction from the cylinders 66 and 84 through the valves 212, 214 and 221 to the sink 202. The springs 52 and 54 furnish the necessary force to return the cutting blade 30 to its non-operative position, while the springs 110 and 112 perform this function for the clamping bar 80 (FIGS. 1 and 3). Thus, the normal position of the cutting blade 30 and the clamping bar 80 is at their upper non-operative attitude. This serves to protect the operator in the event of a hydraulic or electrical failure. In such instances, the blade and clamping bar will always return to the upper position.

The operation of the valve 221, which removes power from the cutting blade 30, provides for very accurate control over the movement of the blade, especially when employed in conjunction with the adjustable stroke feature of the cylinder 66. Both valves 214 and 212 are spring loaded, so that their control members 218 and 216 return to the position illustrated in FIG. 7 as soon as manual pressure is released. The operation cycle including first clamping and then cutting can be repeated only by the actuation of both valves a second time, after the valve 218 has been reset.

The cylinder 82 (FIGS. 3 and 7), which is provided for low pressure clamping, is controlled by a valve 270, operated by a foot switch 272 (FIGS. 1 and 7). The valve 270 is connected by a line 274 from the line 208 to the line 278, which is connected to the cylinder 82, to force the clamping bar 80 downwardly into clamping position. The pressure of the fluid provided by the pump 206 is sufficiently low so that there is no danger of injury to the operator's fingers should they be trapped underneath the clamping bar 80. The foot switch 272 and the cylinder 82 are normally employed by the operator in order to properly position the sheet material for cutting. When the foot switch 272 is not actuated, the line 278 is connected through the valve 270 to a line 279 which communicates with the sink 262 so that the piston 280 is free to move within the cylinder 82 when the clamping bar 80 is operated by the cylinder 84. The end of the cylinder 82 which is not connected to the line 278 is connected via line 281 to the sink 262.

A valve 280 (FIGS. 1 and 7) is located on the front of the machine adjacent the control member 218 of the valve 214. This valve controls ejection of the anvil 155. Upon actuation of the valve 280, pressurized fluid is conveyed to the interior of the expandable tube 156, as has been described hereinbefore in connection with FIGS. 5 and 6. As the tube 156 expands, it pushes the anvil 155 upwardly above the surface of the bed 10, where the anvils position can be changed or the anvil can be replaced by a new anvil.

A valve 276 is provided for control of the cylinder 123 (FIGS. 4 and 7), by which the feed is powered. The cylinder 123 moves the pusher plate 128 toward the area under the cutting blade 30, so that one or more sheets of material may be correctly positioned for cutting. The valve 276 gives the cylinder 123 a reversible capability so that the operating shaft 125 connected to the piston within the cylinder 123 is driven forward, and later rearwardly to resume its starting position. The valve 276 connects a selected end of the cylinder 123 to the line 208 and the other end to the sink 262 via a line 283. A control mechanism 282 is connected with the valve 276 and has adjustable means for providing a fast speed of advancement of the pusher plate 128, and a slower creeping speed for fine adjustment of the position of the sheet material on the bed 10. The details of the valve 276 and the control mechanism 282 are well known to those skilled in the art and therefore need not be specifically described herein. The control mechanism 282 is located adjacent the control member 216 of the valve 212 (FIG. 1)

Referring now to FIG. 8, the cylinder 66, shown in FIG. 1, is illustrated in crosssection, showing the arrangement for providing a variable stroke. The inlet for the fluid is by way of tube 71, which enters the cylinder through a threaded connector 300 in an end wall 301 thereof. A piston 302 is slidably mounted inside the cylinder 66 and has attached thereto the operating shaft 64 (FIG. 1) by means of which the cutting blade 30 is forced downwardly toward the bed 10. The end wall 304 of the cylinder is provided with an aperture having threads 306, and a sleeve 308 surrounds the shaft 64 within that aperture. The sleeve 308 is adjustably positioned with respect to the wall 304 by means of threads on the sleeve which cooperate with the threads 306. Gaskets 310, 312 and 314 provide against leakage from within the cylinder 66 around the shaft 64 or the sleeve 308. The inner end of the sleeve 308 terminates in a flange portion 316, which is adapted to receive and stop the movement of the piston 302. The position of the flange 316 within the cylinder 66 establishes the maximum stroke that the cylinder 66 can produce. A wheel 70, secured to the outer end of the sleeve 308, adjusts the flange position and, thus, the stroke of the cutting blade 30.

The operator of the cutting apparatus must use both hands in controlling the valves 214 and 216, in order to effect the cutting operation. Therefore, the operator must be positioned in front of the machine, and the position of the pusher plate 128 is not readily visible to the operator. Accordingly, a visual indicator 320, illustrated in FIG. 1, is provided to indicate the precise position of the pusher plate 128. The visual indicator 320 may be constructed with lenses and mirrors to show the operator either the position of the pusher plate 128 or an edge of the sheet material being cut. As such apparatus is well known to those skilled in the art, it is not specifically described herein.

The apparatus disclosed herein has been described particularly with reference to a sheet cutting machine for cutting a stack of sheet material at one time. It will be obvious to those skilled in the art, however, that the principles herein disclosed may be applied to other apparatus within the scope of the present invention. It is intended that the claims include any such apparatus and modifications as fall within the spirit of this invention.

What is claimed is:

1. Apparatus for cutting sheet material comprising:

1. a bed for supporting the sheet material;

2. first hydraulically operated means for clamping said sheet material to said bed;

3. a cutting blade;

4. second hydraulically operated means for actuating said cutting blade downwardly through said sheet material;

5. a hydraulic control system for controlling the operation of said clamping means and said blade including a. a first source of fluid under pressure,

b. a first manually operated valve means hydraulically connected to said first source of fluid,

c. a second manually and hydraulically operated valve means hydraulically connected to said first valve means and to said first and second hydraulically operated means,

d. said first valve means adapted to selectively transmit said fluid to said second valve means,

e. said second valve means movable to a first position for transmitting said fluid from said first valve means to said first hydraulically operated means to actuate said clamping means whereby the pressure of said fluid increases from a lower pressure to a higher pressure as the actuation of said clamping means is complete,

. said second valve means manually movable to a second position as said fluid attains said higher pressure whereby said fluid is transmitted to said second hydraulically operated means.

2. Apparatus for cutting sheet material comprising: a bed for supporting the sheet material, hydraulically operated means for clamping said sheet material to said bed, a cutting blade, hydraulically operated means for actuating said cutting blade downwardly through said sheet material,

said bed including a U-shaped channel member disposed below said blade with the open end of said U-shaped channel member even with the upper surface of said bed, a rigid plate supported within said channel, a resilient anvil supported by said plate with its top surface even with the upper surface of said bed, inflatable tube means disposed within said U-shaped channel below said rigid plate, and means for selectively inflating said tube to force said plate and said anvil upwardly and raise said anvil above the upper surface of said bed.

3. Apparatus for cutting sheet material comprising: a bed for supporting the sheet material, hydraulically operated means for clamping said sheet material to said bed, a cutting blade, hydraulically operated means for actuating said cutting blade downwardly through said sheet material,

said blade actuating means including a source of pressurized fluid, a hydraulic power cylinder connected to said blade,

said hydraulic power cylinder comprising a hollow cylindrical body, a piston adapted for longitudinal sliding movement within said cylinder, an operating shaft connected to said piston and extending through a wall closing one end of said body, and a stop sleeve surrounding said shaft at said one end, said sleeve having threads adapted to cooperate with corresponding threads provided in said wall, the inner end of said sleeve being adapted to engage and stop said piston at a position determined by the position of said sleeve relative to said wall.

4. The apparatus of claim 1 wherein the apparatus includes a supporting frame and said blade actuating means includes a pair of links each pivotally connected to said frame so that said blade pivots simultaneously about spaced apart axes as it moves downwardly through said sheet material, means associated with at least one of said links for adjusting the length of said link whereby the attitude of said blade may be regulated.

5. The apparatus of claim 1 including:

third valve means hydraulically connected to said second valve means and to said second hydraulically operated means for preventing said fluid from being transmitted to said second hydraulically operated means until said fluid reaches a predetermined pressure.

6. The apparatus of claim 1 including:

additional hydraulically operated means operably connected to said means for clamping said sheet material to said bed;

a second source of fluid supplying said fluid at a pressure less than the pressure of said first source of fluid; and

additional manually operated valve means for selectively transmitting fluid at said lesser pressure to said additional hydraulically operated means.

7. The apparatus of claim 1 including:

releasable stop means associated with said second valve biased to positively hold said second valve means in said first position;

said releasable stop means adapted to move against said bias under the influence of said fluid at said second higher pressure whereby said second valve means is permitted to move to said second position under the influence of said manual operation. 

1. Apparatus for cutting sheet material comprising:
 1. a bed for supporting the sheet material;
 2. first hydraulically operated means for clamping said sheet material to said bed;
 3. a cutting blade;
 4. second hydraulically operated means for actuating said cutting blade downwardly through said sheet material;
 5. a hydraulic control system for controlling the operation of said clamping means and said blade including a. a first source of fluid under pressure, b. a first manually operated valve means hydraulically connected to said first source of fluid, c. a second manually and hydraulically operated valve means hydraulically connected to said first valve means and to said first and second hydraulically operated means, d. said first valve means adapted to selectively transmit said fluid to said second valve means, e. said second valve means movable to a first position for transmitting said fluid from said first valve means to said first hydraulically operated means to actuate said clamping means whereby the pressure of said fluid increases from a lower pressure to a higher pressure as the actuation of said clamping means is complete, f. said second valve means manually movable to a second position as said fluid attains said higher pressure whereby said fluid is transmitted to said second hydraulically operated means.
 2. first hydraulically operated means for clamping said sheet material to said bed;
 2. Apparatus for cutting sheet material comprising: a bed for supporting the sheet material, hydraulically operated means for clamping said sheet material to said bed, a cutting blade, hydraulically operated means for actuating said cutting blade downwardly through said sheet material, said bed including a U-shaped channel member disposed below said blade with the open end of said U-shaped channel member even with the upper surface of said bed, a rigid plate supported within said channel, a resilient anvil supported by said plate with its top surface even with the upper surface of said bed, inflatable tube means disposed within said U-shaped channel below said rigid plate, and means for selectively inflating said tube to force said plate and said anvil upwardly and raise said anvil above the upper surface of said bed.
 3. Apparatus for cutting sheet material comprising: a bed for supporting the sheet material, hydraulically operated means for clamping said sheet material to said bed, a cutting blade, hydraulically operated means for actuating said cutting blade downwardly through said sheet material, said blade actuating means including a source of pressurized fluid, a hydraulic power cylinder connected to said blade, said hydraulic power cylinder comprising a hollow cylindrical body, a piston adapted for longitudinal sliding movement within said cylinder, an operating shaft connected to said piston and extending through a wall closing one end of said body, and a stop sleeve surrounding said shaft at said one end, said sleeve having threads adapted to cooperate with corresponding threads provided in said wall, the inner end of said sleeve being adapted to engage and stop said piston at a position determined by the position of said sleeve relative to said wall.
 3. a cutting blade;
 4. second hydraulically operated means for actuating said cutting blade downwardly through said sheet material;
 4. The apparatus of claim 1 wherein the apparatus includes a supporting frame and said blade actuating means includes a pair of links each pivotally connected to said frame so that said blade pivots simultaneously about spaced apart axes as it moves downwardly through said sheet material, means associated with at least one of said links for adjusting the length of said link whereby the attitude of said blade may be regulated.
 5. a hydraulic control system for controlling the operation of said clamping means and said blade including a. a first source of fluid under pressure, b. a first manually operated valve means hydraulically connected to said first source of fluid, c. a second manually and hydraulically operated valve means hydraulically connected to said first valve means and to said first and second hydraulically operated means, d. said first valve means adapted to selectively transmit said fluid to said second valve means, e. said second valve means movable to a first position for transmitting said fluid from said first valve means to said first hydraulically operated means to actuate said clamping means whereby the pressure of said fluid increases from a lower pressure to a higher pressure as the actuation of said clamping means is complete, f. said second valve means manually movable to a second position as said fluid attains said higher pressure whereby said fluid is transmitted to said second hydraulically operated means.
 5. The apparatus of claim 1 including: third valve means hydraulically connected to said second valve means and to said second hydraulically operated means for preventing said fluid from being transmitted to said second hydraulically operated means until said fluid reaches a predetermined pressure.
 6. The apparatus of claim 1 including: additional hydraulically operated means operably connected to said means for clamping said sheet material to said bed; a second source of fluid supplying said fluid at a pressure less than the pressure of said first source of fluid; and additional manually operated valve means for selectively transmitting fluid at said lesser pressure to said additional hydraulically operated means.
 7. The apparatus of claim 1 including: releasable stop means associated with said second valve biased to positively hold said second valve means in said first position; said releasable stop means adapted to move against said bias under the influence of said fluid at said second higher pressure whereby said second valve means is permitted to move to said second position under the influence of said manual operation. 